Evacuated sample collection tubes have been in general usage in the United States for almost fifty years. Initially, as disclosed in U.S. Pat. No. 2,460,641 to Klienert, the sample collection tube was simply an evacuated glass test tube with a resilient stopper and intended for use in blood collection. As practitioners recognized the utility of these evacuated blood collection tubes, (trade named "Vacutainer" and available from Becton, Dickinson and Company, Franklin Lakes, N.J.) the tubes are now supplied with various additives already in them to prepare the blood specimen for a particular test. The tubes are also evacuated to selected less than atmospheric pressures to provide a preselected volume of blood drawn. The most widely used tubes are evacuated to provide a blood withdrawal volume between about four and one half milliliters to about ten milliliters.
Practitioners recognized the need for tubes with smaller capacity than the standard tubes and several alternative smaller tubes are available. U.S. Pat. No. 4,397,318 discloses a smaller tube termed a "microcollection tube" with a blood collector top. U.S. Pat. No. 5,384,096 also discloses a microcollection tube assembly that includes an adapter portion mounted on the closed end of the tube to facilitate handling of the small microcollection tube.
After the samples are collected in blood collection tubes, many of the tubes are used in some type of automated laboratory equipment ranging from centrifuges to automatic samplers and auto analyzers. Most of these automated devices are designed to accept the standard 13 mm.times.100 mm or 16 mm.times.100 mm tubes. Thus, the smaller microcollection tubes are not well suited to be used with much of the available automated equipment.
In an effort to address the handling problems, U.S. Pat. No. 5,384,096 discloses an adapter portion that serves to facilitate handling of the microcollection tube. Additionally, with the advent of blood collection tubes formed by injection molding of polymeric materials, standard sized tubes have been made available with reduced capacity reservoirs. These small capacity standard size tubes are molded with a large recess in the closed end. These tubes are more difficult to form by injection molding than a conventional "test-tube" shape and some of them do not feed particularly well through automated sampling equipment. The efficiency of forming and assembling different parts or molding more difficult shapes is less than the efficiency of forming more standard shaped blood collection tubes. Also, whenever there is device with more than one part, the manufacturing efficiency is reduced not only by the need to assemble the parts, maintain an inventory of separate parts as well as by the need for separate tooling and forming machinery for each part.
If a reduced capacity blood collection tube was available that only required one part, provided the desired sample draw capacity and additionally was compatible with automated sampling and analysis equipment, the art of blood sampling and analysis would be advanced. Such a blood collection tube is disclosed hereinbelow.